Abstarct: Loop heat pipe is a passive heat exchanger without moving mechanical device that are very suitable for transfer heat to medium fluxes with the lowest cost and highest performance in the smallest space. In this study, the performance of loop heat pipe in heat exchangers has been investigated empirically. Loop heat pipe is formant of pipes with small diameter which after discharge the air inside of that, fill the evaporator section of the working fluid, partially. Unlike conventional type which its pipes has a wick tubes in all parts, these heat pipes only have wick in the evaporator section. The model used in this tube is in the form of a Loop-shaped and at the top is the condenser, and the bottom is evaporator, and the interface between these two parts is narrow-diameter insulation pipes. The required heat flux is provided by torch. Hot air is driven into the channel of the evaporator section by a haustellate fan. For cooling, the blower fan has been used to direct cool air to the condenser section of the channel. Also in this system, the working fluid of pure water has been used and the structure and pipes are made of copper with high purity. The evaporator wick by using powder mextallurgy technology has been made of copper, as well as these experiment, were investigated in the absence of the wick and a comparison was made between the two modes. In this study, the cold air mass flow rate is fixed and the effects of mass flow, hot smoke and the inlet temperature of hot smoke was examined on system performance and thermal analysis was done. The results show that increasing the flow rate of hot air decreases the temperature difference between the inlet and the outlet temperature of hot smoke channel and on the other hands, increasing the temperature of input hot smoke causes increasing the difference of input and output temperature of both channels. Increasing the mass flow rate of hot smoke reduces the system's energy efficiency, however, increasing the temperature of the system, does not necessarily result in increased efficiency Also, an important issue that occurs in the absence of the wick is low startup time of system, the duration of the pre-heating of system is too long. And also it is clear that with respect to the wick system, the efficiency is lower because we have more heat dissipation, because of the low thermal conductivity and low capillary level, system receives less heat from the system. The obtained data show that the efficiency of the system until the speed of input hot smoke to the evaporator section reaches to 3.3 meters per second is going down with a gentle slope. And from this speed to the next, efficiency decreases with a steeper slope and at some speed, and in particular powers faced with sharp loss of efficiency.